Wafer processing method

ABSTRACT

A wafer processing method includes: a protective member providing step of providing a protective member on the front side of a wafer; a wafer quarter generating step of cutting the wafer along the division line extending in a first direction through the center of the wafer and along the division line extending in a second direction perpendicular to the first direction through the center of the wafer, thereby generating four sectorial wafer quarters; a back grinding step of grinding the back side of each wafer quarter to reduce the thickness of the wafer quarter; a frame providing step of supporting the wafer quarter through an adhesive tape to an annular frame; and a wafer quarter dividing step of fully cutting the wafer quarter along all of the division lines extending in the first and second directions, thereby dividing the wafer quarter into the individual devices.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wafer processing method which canprocess a large-diameter wafer by using existing equipment to themaximum.

2. Description of the Related Art

A plurality of crossing division lines are formed on the front side of asemiconductor wafer (which will be hereinafter referred to also simplyas wafer) to thereby partition a plurality of regions where a pluralityof devices such as ICs and LSIs are respectively formed. The back sideof the wafer is ground to reduce the thickness of the wafer to a desiredthickness. Thereafter, the wafer is divided along the division lines toobtain the individual devices, which are widely used in variouselectrical equipment such as mobile phones and personal computers.

In dividing the semiconductor wafer, a cutting apparatus called a dicingapparatus is widely used. The dicing apparatus includes a chuck tablefor holding the wafer and cutting means for rotatably supporting acutting blade. The wafer is supported through a dicing tape to anannular frame prior to holding the wafer on the chuck table. To improvethe productivity, the diameter of the wafer tends to be increased as to200 mm, 300 mm, and 450 mm. Accordingly, it is essential to develop aprocessing apparatus such as a dicing apparatus and a grinding apparatusconforming to such a large-diameter wafer.

SUMMARY OF THE INVENTION

However, in the case of processing a wafer having a diameter of 450 mm,a new system must be constructed by using a processing apparatusconforming to a 450 mm wafer in spite of the fact that there has alreadybeen provided equipment for grinding the back side of a 300-mm wafer todivide the wafer into individual devices. As a result, equipment costsbecome very high to cause a squeeze on profits.

It is therefore an object of the present invention to provide a waferprocessing method which can use existing equipment even in the case of alarge-diameter wafer.

In accordance with an aspect of the present invention, there is provideda wafer processing method for dividing a wafer into a plurality ofindividual devices along a plurality of division lines extending in afirst direction on the front side of the wafer and a plurality ofdivision lines extending in a second direction perpendicular to thefirst direction on the front side of the wafer, the individual devicesbeing respectively formed in a plurality of regions partitioned by thedivision lines extending in the first direction and the division linesextending in the second direction, the wafer processing method includinga protective member providing step of providing a protective member onthe front side of the wafer; a wafer quarter generating step of cuttingthe wafer along the division line extending in the first directionthrough the center of the wafer and along the division line extending inthe second direction through the center of the wafer after performingthe protective member providing step, thereby generating four sectorialwafer quarters; a back grinding step of grinding the back side of eachwafer quarter to reduce the thickness of the wafer quarter afterperforming the wafer quarter generating step; a frame providing step ofpreparing an annular frame having an opening capable of accommodatingthe wafer quarter after performing the back grinding step, next placingthe wafer quarter in the opening of the annular frame, next attaching anadhesive tape to the annular frame and the back side of the waferquarter, and next peeling the protective member from the front side ofthe wafer quarter, thereby supporting the wafer quarter through theadhesive tape to the annular frame; and a wafer quarter dividing step offully cutting the wafer quarter along all of the division linesextending in the first direction and along all of the division linesextending in the second direction after performing the frame providingstep, thereby dividing the wafer quarter into the individual devices.

According to the wafer processing method of the present invention, atleast one cutting apparatus conforming to a large-diameter wafer isrequired to divide the large-diameter wafer into four wafer quarters.However, existing apparatuses conforming to a small-diameter wafer canbe used as a grinding apparatus for grinding the back side of each waferquarter and a dicing apparatus for dividing each wafer quarter intoindividual devices. Accordingly, it is unnecessary to construct a newsystem conforming to a large-diameter wafer, and existing equipment canbe used to the maximum to thereby save equipment costs.

The above and other objects, features and advantages of the presentinvention and the manner of realizing them will become more apparent,and the invention itself will best be understood from a study of thefollowing description and appended claims with reference to the attacheddrawings showing a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a semiconductor wafer (450-mm wafer) asviewed from the front side thereof;

FIG. 2 is a perspective view showing a manner of attaching a protectivetape to the front side of the wafer shown in FIG. 1;

FIG. 3 is a perspective view showing a manner of holding the wafer withthe protective tape shown in FIG. 2 on a chuck table conforming to a450-mm wafer;

FIG. 4 is a perspective view showing a wafer quarter generating stepusing the chuck table shown in FIG. 3;

FIG. 5 is a perspective view of four wafer quarters obtained by thewafer quarter generating step shown in FIG. 4;

FIG. 6 is a perspective view showing a manner of holding each waferquarter shown in FIG. 5 on a chuck table having a suction holdingportion corresponding to each wafer quarter;

FIG. 7 is a perspective view showing a back grinding step using thechuck table shown in FIG. 6;

FIG. 8 is a perspective view showing a frame providing step;

FIG. 9 is a perspective view showing a wafer quarter dividing step; and

FIG. 10 is a perspective view of each wafer quarter divided intoindividual devices by the wafer quarter dividing step shown in FIG. 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the present invention will now be describedwith reference to the drawings. FIG. 1 shows a semiconductor wafer 11 tobe processed by the wafer processing method according to this preferredembodiment. The semiconductor wafer 11 shown in FIG. 1 is a siliconwafer having a thickness of 700 μm, for example. As shown in FIG. 1, thesemiconductor wafer 11 has a front side 11 a and a back side 11 b.Further, a plurality of crossing division lines (streets) 13 are formedon the front side 11 a of the semiconductor wafer 11, therebypartitioning a plurality of regions where a plurality of devices 15 arerespectively formed. The wafer 11 has a diameter of 450 mm. There willnow be described the wafer processing method according to this preferredembodiment for dividing the 450-mm wafer 11 as a large-diameter waferinto the individual devices 15 by using existing equipment to themaximum, with reference to FIGS. 2 to 10.

As shown in FIG. 2, a protective member providing step is firstperformed in such a manner that a protective member is provided on thefront side 11 a of the wafer 11. More specifically, a circularprotective tape 21 as the protective member is attached to the frontside 11 a of the wafer 11. In this preferred embodiment, the protectivetape 21 is formed of a transparent resin. As a modification, atransparent glass plate as the protective member may be attached to thefirst side 11 a of the wafer 11 in place of the transparent protectivetape 21.

After performing the protective member providing step mentioned above, awafer quarter generating step is performed by using a chuck table 10shown in FIG. 3. This chuck table 10 is a chuck table in a dicingapparatus (cutting apparatus) conforming to the 450-mm wafer 11. Thatis, the chuck table 10 has a size (diameter) capable of holding the450-mm wafer 11 under suction.

The chuck table 10 includes a frame 12 formed of stainless steel or thelike. The frame 12 has an annular upper surface 12 a and a cross-shapedupper surface 12 b formed inside the annular upper surface 12 a. Thecross-shaped upper surface 12 b is formed with two straight reliefgrooves 14 intersecting at right angles to each other at the center ofthe annular upper surface 12 a. Each relief groove 14 has apredetermined depth. The chuck table 10 further includes four sectorialsuction holding portions 16 surrounded by the annular upper surface 12 aand the cross-shaped upper surface 12 b of the frame 12. Each suctionholding portion 16 is formed of porous ceramic or the like.

The wafer quarter generating step using the chuck table 10 is performedby cutting the wafer 11 along the division line 13 extending in a firstdirection through the center of the wafer 11 and along the division line13 extending in a second direction perpendicular to the first directionthrough the center of the wafer 11, thereby generating four sectorialwafer quarters 11A, 11B, 11C, and 11D (see FIG. 5). In this waferquarter generating step, the wafer 11 is held on the chuck table 10under suction as shown in FIG. 4. The cutting apparatus having the chucktable 10 includes a cutting unit 18 shown in FIG. 4. The cutting unit 18includes a spindle (not shown) rotatably supported and driven in aspindle housing 20, a cutting blade 22 mounted on the front end of thespindle, and a blade cover 24 for covering the upper half of the cuttingblade 22.

The wafer quarter generating step is performed in the following manner.First, the cutting blade 22 is rotated at a high speed and lowered tocut into one end of the division line 13 extending in the firstdirection through the center of the wafer 11. Thereafter, the chucktable 10 is moved in the direction (feeding direction) shown by an arrowX1 in FIG. 4 to thereby completely cut the wafer 11 into two parts alongthis division line 13. In this complete cutting of the wafer 11, theouter circumference of the cutting blade 22 reaches a vertical positionbelow the back side of the wafer 11. However, since the relief groove 14is formed on the chuck table 10 so as to extend along this division line13, there is no possibility that the cutting blade 22 may be damaged.Thereafter, the chuck table 10 is rotated 90° to similarly cut the wafer11 along the division line 13 extending in the second direction throughthe center of the wafer 11, thereby obtaining the four sectorial waferquarters 11A, 11B, 11C, and 11D shown in FIG. 5.

As described above, the protective tape 21 is formed of a transparentresin in this preferred embodiment. Accordingly, an alignment operationcan be performed by using a normal imaging device (visible light) tomake the alignment of the division line 13 to be cut and the cuttingblade 22. In the case that the protective tape 21 is formed of an opaqueresin, the front side 11 a of the wafer 11 can be imaged through theprotective tape 21 by using an infrared imaging device (infrared light)of an imaging unit provided in the cutting apparatus, thereby making thealignment of the division line 13 to be cut and the cutting blade 22.

After performing the wafer quarter generating step mentioned above, aback grinding step is performed by using a chuck table 30 shown in FIG.6. FIG. 6 is a perspective view showing a manner of holding the waferquarter 11A with the protective tape 21 on the chuck table 30. The chucktable 30 has a sectorial suction holding portion 32 corresponding to thewafer quarter 11A. The chuck table 30 is mounted in a grinding apparatusconforming to a 300-mm wafer.

The back grinding step using the chuck table 30 is performed in thefollowing manner. As shown in FIG. 7, the wafer quarter 11A is heldthrough the protective tape 21 on the chuck table 30 in the conditionwhere the back side 11 b of the wafer quarter 11A is exposed. As shownin FIG. 7, the grinding apparatus includes a grinding unit 34. Thegrinding unit 34 includes a spindle 36 adapted to be rotationallydriven, a wheel mount 38 fixed to the lower end of the spindle 36, and agrinding wheel 40 detachably mounted on the lower surface of the wheelmount 38 by a plurality of screws 42. The grinding wheel 40 is composedof an annular wheel base 44 and a plurality of abrasive members 46 fixedto the lower surface of the wheel base 44 along the outer circumferencethereof so as to be arranged annularly at given intervals.

In performing the back grinding step of grinding the back side 11 b ofthe wafer quarter 11A to thereby reduce the thickness of the waferquarter 11A, the chuck table 30 holding the wafer quarter 11A throughthe protective tape 21 under suction is rotated at 300 rpm, for example,in the direction shown by an arrow a in FIG. 7 and the grinding wheel 40is also rotated at 6000 rpm, for example, in the direction shown by anarrow b in FIG. 7. In this rotational condition, the abrasive members 46of the grinding wheel 40 are brought into contact with the back side 11b of the wafer quarter 11A, and the grinding wheel 40 is fed downward ata predetermined feed speed (e.g., 1 μm/s), thereby grinding the backside 11 b of the wafer quarter 11A to reduce the thickness of the waferquarter 11A to a predetermined thickness. The back grinding step issimilarly performed to all of the other wafer quarters 11B to 11D.

After performing the back grinding step mentioned above, a frameproviding step is performed in the following manner. As shown in FIG. 8,an annular frame F having an opening capable of accommodating the waferquarter 11A is prepared and the wafer quarter 11A is placed in theopening of the annular frame F. In this condition, an adhesive tape T isattached to the annular frame F and the back side 11 b of the waferquarter 11A. Thereafter, the protective tape 21 is peeled from the frontside 11 a of the wafer quarter 11A to thereby support the wafer quarter11A through the adhesive tape T to the annular frame F. The frameproviding step is similarly performed to all of the other wafer quarters11B to 11D.

After performing the frame providing step mentioned above, a waferquarter dividing step is performed to divide the wafer quarter 11A intothe individual devices 15 by using a cutting unit 18A of a cuttingapparatus conforming to a 300-mm wafer as shown in FIG. 9. In this waferquarter dividing step, the wafer quarter 11A supported through theadhesive tape T to the annular frame F is held on a chuck table (notshown) under suction. Thereafter, the cutting blade 22 of the cuttingunit 18A is rotated at a high speed and lowered to cut into the waferquarter 11A so as to reach the adhesive tape T at one end of apredetermined one of the division lines 13 extending in the firstdirection. Thereafter, the chuck table (not shown) is moved in thedirection (feeding direction) shown by an arrow X1 in FIG. 9 to therebyform a full-cut groove 19 along the predetermined division line 13extending in the first direction.

This wafer quarter dividing step is similarly performed along all of theother division lines 13 extending in the first direction to thereby forma plurality of similar full-cut grooves 19. Thereafter, the chuck tableis rotated 90° to similarly form the wafer quarter dividing step alongall of the division lines 13 extending in the second direction, therebyforming a plurality of similar full-cut grooves 19. As a result, thewafer quarter 11A is divided into the individual devices 15 as shown inFIG. 10. The wafer quarter dividing step is similarly performed to allof the other wafer quarters 11B to 11D. Although not shown, a pickupstep is next performed to pick up each device 15 from the adhesive tapeT by using a pickup collet, for example.

According to the wafer processing method of the present invention, atleast one cutting apparatus conforming to a large-diameter wafer such asa 450-mm wafer is required to divide the large-diameter wafer into fourwafer quarters. However, existing apparatuses conforming to asmall-diameter wafer such as a 300-mm wafer can be used as a grindingapparatus for grinding the back side of each wafer quarter and a dicingapparatus (cutting apparatus) for dividing each wafer quarter intoindividual devices. Accordingly, it is unnecessary to construct a newsystem conforming to a large-diameter wafer, and existing equipment canbe used to the maximum to thereby save equipment costs.

The present invention is not limited to the details of the abovedescribed preferred embodiment. The scope of the invention is defined bythe appended claims and all changes and modifications as fall within theequivalence of the scope of the claims are therefore to be embraced bythe invention.

What is claimed is:
 1. A wafer processing method for dividing a waferhaving a diameter of at least about 450 mm into a plurality ofindividual devices along a plurality of division lines extending in afirst direction on a front side of said wafer and a plurality ofdivision lines extending in a second direction perpendicular to saidfirst direction on the front side of said wafer, said individual devicesbeing respectively formed in a plurality of regions partitioned by saiddivision lines extending in said first direction and said division linesextending in said second direction, said wafer processing methodcomprising: a protective member providing step of providing a protectivemember on the front side of said wafer; a first holding step of holdingsaid wafer with said protective member provided on the front side ofsaid wafer by a first chuck table having two straight relief groovesintersecting at right angles to each other at the center of an uppersurface of said chuck table and four sectional suction holding portionspartitioned by said relief grooves; a wafer quarter generating step ofcutting said wafer and the protective member along said division lineextending in said first direction through the center of said wafer andalong said division line extending in said second direction through thecenter of said wafer after performing said protective member providingstep, thereby generating four sectorial wafer quarters; a second holdingstep of holding said wafer quarter by a second chuck table having asectorial suction holding portion corresponding to said wafer quarter,said second chuck table being mounted in a grinding apparatus configuredfor holding a wafer with a diameter no greater than 300 mm; a backgrinding step of grinding a back side of a single wafer quarter toreduce the thickness of said wafer quarter after performing said waferquarter generating step; a frame providing step of preparing an annularframe having an opening capable of accommodating said wafer quarterafter performing said back grinding step, next placing said waferquarter in said opening of said annular frame, next attaching anadhesive tape to said annular frame and a back side of said waferquarter, and next peeling said protective member from the front side ofsaid wafer quarter, thereby supporting said wafer quarter through saidadhesive tape to said annular frame; and a wafer quarter dividing stepof fully cutting said wafer quarter along all of said division linesextending in said first direction and along all of said division linesextending in said second direction after performing said frame providingstep, thereby dividing said wafer quarter into said individual devices,whereby said at least about 450 mm wafer exceeds a wafer diameter sizethat can be held on said second chuck table configured for holding awafer with a diameter no greater than 300 mm.